Diamonds are weighed to the thousandth (.001) of a carat (ct) and then rounded to the nearest hundredth (.01). The weight will only be rounded up to the nearest hundredth if the thousandth digit is a nine. For example, a stone that weighs 1.768 ct would be rounded to 1.76 ct, but one that weighs 1.769 ct would be rounded to 1.77 ct.
